Use the Autoconf macro AC_USE_SYSTEM_EXTENSIONS

The Autoconf macro AC_USE_SYSTEM_EXTENSIONS defines preprocessor macros
which turn on extensions to C and POSIX. The macro also makes it easier
for developers to use the extensions without needing (or forgetting) to
define them manually.

The macro can be safely used because it was introduced in Autoconf 2.60
and Tor requires Autoconf 2.63 and above.

12 files changed, 7 insertions, 44 deletions

diff --git a/changes/bug19139 b/changes/bug19139
new file mode 100644
index 0000000000..2e53d7d445
--- /dev/null
+++ b/changes/bug19139
@@ -0,0 +1,3 @@
+  o Minor features (build):
+    - Use the Autoconf macro AC_USE_SYSTEM_EXTENSIONS to automatically
+      turn on C and POSIX extensions. Closes ticket 19139.
diff --git a/configure.ac b/configure.ac
index 386fcdd132..6d721a2fc5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -16,6 +16,7 @@ AM_INIT_AUTOMAKE([foreign 1.11 subdir-objects])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 AC_CONFIG_HEADERS([orconfig.h])
 
+AC_USE_SYSTEM_EXTENSIONS
 AC_CANONICAL_HOST
 
 PKG_PROG_PKG_CONFIG
@@ -1552,9 +1553,6 @@ int main(int c, char **v) { puts(__FUNCTION__); }])],
 AC_CACHE_CHECK([whether we have extern char **environ already declared],
   tor_cv_have_environ_declared,
   AC_COMPILE_IFELSE([AC_LANG_SOURCE([
-/* We define _GNU_SOURCE here because it is also defined in compat.c.
- * Without it environ doesn't get declared. */
-#define _GNU_SOURCE
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
diff --git a/m4/pc_from_ucontext.m4 b/m4/pc_from_ucontext.m4
index 6bedcbb2da..8a9dc459e6 100644
--- a/m4/pc_from_ucontext.m4
+++ b/m4/pc_from_ucontext.m4
@@ -79,24 +79,21 @@ AC_DEFUN([AC_PC_FROM_UCONTEXT],
      if ! $pc_field_found; then
        # Prefer sys/ucontext.h to ucontext.h, for OS X's sake.
        if test "x$ac_cv_header_cygwin_signal_h" = xyes; then
-         AC_TRY_COMPILE([#define _GNU_SOURCE 1
-                         #include <cygwin/signal.h>],
+         AC_TRY_COMPILE([#include <cygwin/signal.h>],
                         [ucontext_t u; return u.$pc_field == 0;],
                         AC_DEFINE_UNQUOTED(PC_FROM_UCONTEXT, $pc_field,
                                            How to access the PC from a struct ucontext)
                         AC_MSG_RESULT([$pc_field])
                         pc_field_found=true)
        elif test "x$ac_cv_header_sys_ucontext_h" = xyes; then
-         AC_TRY_COMPILE([#define _GNU_SOURCE 1
-                         #include <sys/ucontext.h>],
+         AC_TRY_COMPILE([#include <sys/ucontext.h>],
                         [ucontext_t u; return u.$pc_field == 0;],
                         AC_DEFINE_UNQUOTED(PC_FROM_UCONTEXT, $pc_field,
                                            How to access the PC from a struct ucontext)
                         AC_MSG_RESULT([$pc_field])
                         pc_field_found=true)
        elif test "x$ac_cv_header_ucontext_h" = xyes; then
-         AC_TRY_COMPILE([#define _GNU_SOURCE 1
-                         #include <ucontext.h>],
+         AC_TRY_COMPILE([#include <ucontext.h>],
                         [ucontext_t u; return u.$pc_field == 0;],
                         AC_DEFINE_UNQUOTED(PC_FROM_UCONTEXT, $pc_field,
                                            How to access the PC from a struct ucontext)
diff --git a/src/common/backtrace.c b/src/common/backtrace.c
index 3b762b68e3..afdc10d6a9 100644
--- a/src/common/backtrace.c
+++ b/src/common/backtrace.c
@@ -13,9 +13,6 @@
  * detect crashes.
  */
 
-#define __USE_GNU
-#define _GNU_SOURCE 1
-
 #include "orconfig.h"
 #include "compat.h"
 #include "util.h"
diff --git a/src/common/compat.c b/src/common/compat.c
index 370881b07e..72dffe2a6e 100644
--- a/src/common/compat.c
+++ b/src/common/compat.c
@@ -12,18 +12,6 @@
  * the platform.
  **/
 
-/* This is required on rh7 to make strptime not complain.
- * We also need it to make memmem get defined (where available)
- */
-
-/* XXXX We should just  use AC_USE_SYSTEM_EXTENSIONS in our autoconf,
- * and get this (and other important stuff!) automatically. Once we do that,
- * make sure to also change the extern char **environ detection in
- * configure.ac, because whether that is declared or not depends on whether
- * we have _GNU_SOURCE defined! Maybe that means that once we take this out,
- * we can also take out the configure check. */
-#define _GNU_SOURCE
-
 #define COMPAT_PRIVATE
 #include "compat.h"
 
diff --git a/src/common/compat_pthreads.c b/src/common/compat_pthreads.c
index 1b24cc3c2a..1d6db34225 100644
--- a/src/common/compat_pthreads.c
+++ b/src/common/compat_pthreads.c
@@ -10,8 +10,6 @@
  * functions.
  */
 
-#define _GNU_SOURCE
-
 #include "orconfig.h"
 #include <pthread.h>
 #include <signal.h>
diff --git a/src/common/compat_threads.c b/src/common/compat_threads.c
index 8f9001258a..9c6fa55b32 100644
--- a/src/common/compat_threads.c
+++ b/src/common/compat_threads.c
@@ -11,8 +11,6 @@
  *  modules.)
  */
 
-#define _GNU_SOURCE
-
 #include "orconfig.h"
 #include <stdlib.h>
 #include "compat.h"
diff --git a/src/common/crypto.c b/src/common/crypto.c
index f47f5d2471..d5043c3246 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -56,7 +56,6 @@ ENABLE_GCC_WARNING(redundant-decls)
 #include <ctype.h>
 #endif
 #ifdef HAVE_UNISTD_H
-#define _GNU_SOURCE
 #include <unistd.h>
 #endif
 #ifdef HAVE_FCNTL_H
diff --git a/src/common/sandbox.c b/src/common/sandbox.c
index 4e2c5cde22..94b2fc6788 100644
--- a/src/common/sandbox.c
+++ b/src/common/sandbox.c
@@ -39,8 +39,6 @@
 
 #if defined(USE_LIBSECCOMP)
 
-#define _GNU_SOURCE
-
 #include <sys/mman.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
diff --git a/src/common/sandbox.h b/src/common/sandbox.h
index 2defd8bbd4..c5963e3119 100644
--- a/src/common/sandbox.h
+++ b/src/common/sandbox.h
@@ -39,12 +39,6 @@ typedef struct sandbox_cfg_elem sandbox_cfg_t;
  */
 #ifdef USE_LIBSECCOMP
 
-#ifndef __USE_GNU
-#define __USE_GNU
-#endif
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE
-#endif
 #include <sys/ucontext.h>
 #include <seccomp.h>
 #include <netdb.h>
diff --git a/src/common/util.c b/src/common/util.c
index 2f7cc4f892..7217cdc81e 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -9,10 +9,6 @@
  * process control.
  **/
 
-/* This is required on rh7 to make strptime not complain.
- */
-#define _GNU_SOURCE
-
 #include "orconfig.h"
 #ifdef HAVE_FCNTL_H
 #include <fcntl.h>
diff --git a/src/ext/eventdns.c b/src/ext/eventdns.c
index 7046f32eb9..f5b7723b54 100644
--- a/src/ext/eventdns.c
+++ b/src/ext/eventdns.c
@@ -50,9 +50,6 @@
 #endif
 #endif
 
-/* #define _POSIX_C_SOURCE 200507 */
-#define _GNU_SOURCE
-
 #ifdef DNS_USE_CPU_CLOCK_FOR_ID
 #ifdef DNS_USE_OPENSSL_FOR_ID
 #error Multiple id options selected